help thermaling mgm 60

today i went and run my T4 to see how fast it is with the new setup, this was the first high speed test. unfortualitly after abut 5 min of running( about 3 high speed passes in a big parking lot) it went into protection. so i have a mgm 60 and a 4200 combo running 8 cells. my question is, is this normal should this be happaning, is 8 cells ot much for this set up. is theri a fix for it a fan or somethin, and how might i go about solving this problem